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[Xen-devel] Re: [RFC, PATCH 1/24] i386 Vmi documentation

* Andi Kleen (ak@xxxxxxx) wrote:
> On Monday 13 March 2006 18:59, Zachary Amsden wrote:
> > +     The general mechanism for providing customized features and
> > +     capabilities is to provide notification of these feature through
> > +     the CPUID call, 
> How should that work since CPUID cannot be intercepted by 
> a Hypervisor (without VMX/SVM)?  

Yeah, it requires guest kernel cooperation/modification.

> > +   The net result of these choices is that most of the calls are very
> > +   easy to make from C-code, and calls that are likely to be required in
> > +   low level trap handling code are easy to call from assembler.   Most
> > +   of these calls are also very easily implemented by the hypervisor
> > +   vendor in C code, and only the performance critical calls from
> > +   assembler paths require custom assembly implementations.
> > +
> Did I miss it or do you never describe how to find these entry points? 

It's the ROM interface.  For native they are emitted directly inline.
For non-native, they are emitted as call stubs, which call to the ROM.
I don't recall if it's in this doc, but the inline patch has all the
gory details.


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